DRUG INDEX
GENERIC NAME: famciclovir BRAND NAME: Famvir
DRUG CLASS AND MECHANISM: Famciclovir is an antiviral drug which is active against the Herpes viruses, including herpes simplex 1 and 2 (cold sores and genital herpes) and varicella-zoster ( shingles and chicken pox). It inhibits the replication of viral DNA that is necessary in order for viruses to reproduce themselves. Famciclovir is actually a "prodrug," in that it is not active directly against viruses. Instead, famciclovir is converted to penciclovir in the body, and it is the penciclovir that is active against the viruses. (Penciclovir also is available as a topical and intravenous medication.) Famciclovir is active against the same viruses as acyclovir but has a longer duration of action. Therefore, it can be taken fewer times each day. Famciclovir was approved for use by the FDA in 1994.
PRESCRIPTION: yes
GENERIC AVAILABLE: no
PREPARATIONS: Tablets (125mg, 250mg, 500mg).
STORAGE: Famciclovir should be kept between 2° and 30°C (36-86° F).
PRESCRIBED FOR: Famciclovir is used to treat the first episode of genital herpes and to treat patients with recurrent (more than 6 episodes per year) severe genital herpes. Famciclovir reduces the pain and the number of sores with the first episode and decreases the frequency and severity of episodes in individuals with recurrent episodes. In the treatment of shingles, famciclovir reduces pain, shortens the time in which sores heal, and limits the spread of virus and the formation of new sores. Famciclovir can be used to treat chicken pox to reduce healing time, limit the number of sores (pox), and reduce fever if used within the first 24 hours after the onset of the disease.
DOSING: Famciclovir may be taken with or without food. Penciclovir, the active metabolite of famciclovir, is excreted mainly by the kidney, and dosages of famciclovir need to be reduced in patients with kidney dysfunction.
DRUG INTERACTIONS: Probenecid (Benemid) may reduce the kidney's clearance of penciclovir leading to higher concentrations of penciclovir in the blood. This may lead to side effects of penciclovir. Using famciclovir with digoxin (Lanoxin) may result in an increase in the concentration of digoxin in the blood. This may lead to side effects of digoxin.
PREGNANCY: Animal studies have not produced effects on the fetus. However, there have been no studies in humans. Famciclovir should only be used during pregnancy when the benefits to the mother outweigh potential risks to the fetus.
NURSING MOTHERS: Studies in rats have shown higher concentrations of penciclovir in breast milk than in blood. It is not known if penciclovir is excreted into human milk. Women may wish to consider an alternative to breast-feeding if famciclovir is taken while nursing.
SIDE EFFECTS: The most common side effects associated with the use of famciclovir are headache, fatigue, nausea, and vomiting. Less common side effects include fever, pain, shaking chills, constipation , loss of appetite, abdominal pain , back pain, joint pain, dizziness , tingling of the extremities, tiredness, sore throat , sinus congestion, and itching.
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